Cases of dengue fever, a mosquito-borne viral illness that can be fatal, are surging around the world. The increase is occurring both in places that have long struggled with the disease and in areas where its spread was unheard-of until the last year or two, including France, Italy and Chad, in central Africa. Last week, health officials in Pasadena, Calif., reported a first case of locally transmitted dengue.
What is dengue fever and why is it becoming more widespread?
Dengue, a viral fever, is transmitted by Aedes species of mosquitoes. It can cause excruciating joint pain; is also known by the grim nickname “breakbone fever.”
The Aedes aegypti mosquito, which has been driving many of the current outbreaks, is native to Africa, where it originally lived in forests and fed on animals. But decades ago it spread to the rest of the world via trade routes and adapted to thrive in urban areas, feeding on people and breeding in small bits of trapped water in places such as old tires, discarded bottle caps and trays used to catch air-conditioner drips.
Now as more people move to urban areas — many to lower-quality housing in developing countries — they are more vulnerable to the virus. And climate change is bringing the mosquito to new places, where it is thriving.